Multi-Stage Rotary Compressor

ABSTRACT

A multi-stage rotary compressor comprises: a casing having a sealed space therein; a driving unit installed in the casing, for generating a driving force; a first compression unit and a second compression unit for receiving the driving force from the driving unit and compressing a refrigerant; and a connection unit for connecting the first and second compression units and guiding the refrigerant discharged from the second compression unit to be sucked directly in the first compression unit and then re-compressed, by which it is possible to vary capacity, even using every plurality of compression units, and to obtain power saving effect suitable for a saving mode.

TECHNICAL FIELD

The present invention relates to a rotary compressor which is compressedin a multi-stage, and more particularly, to a multi-stage rotarycompressor capable of optimizing compression efficiency, using aplurality of compression units all together.

BACKGROUND ART

A compressor is a device for compressing an operation gas and thusenhancing pressure by receiving power from a power generator such as anelectric motor and compressing air, a refrigerant gas or other specificgas, which has been being used throughout industries. The compressor maybe divided into a positive displacement compressor and a turbocompressor according to how to compress. The positive displacementcompressor has a compressing method in which pressure is increased bydecreasing volume, while the turbo compressor achieves a compression byconverting a kinetic energy of a gas into a pressing energy. A rotarycompressor, one of the positive displacement compressor, is generallyapplied to an air conditioning apparatus such as an air-conditioner.Recently, it is the trend that the air-conditioner has variousfunctions. In response, the rotary compressor requires a product capableof varying capacity thereof.

The rotary compressor has used a refrigerant containing a CFC-basedchlorine. However, the refrigerant is known to destroy the earth's ozonelayer, which causes a global warming. As a result, its use is legallyregulated and extensive researches have been made for an alternativerefrigerant with respect to the existing refrigerant. Carbon dioxide isexpected as the alternative refrigerant. Moreover, the global warming isled to a problem of improvement of an energy efficiency of instrumentsas well as a problem of the alternative of the refrigerant. This isbecause the carbon dioxide occurred by burning fossil fuel (a great dealof electric energy is still obtained by burning the fossil fuel) is thechief culprit of the global warming.

Accordingly, in the compressor which corresponds to the core part of arefrigeration system, it is the most considerable matter how to applyingalternative refrigerants harmless for a global environment to theexisting compressor without loss of performance thereof.

There is a multi-stage rotary compressor having a plurality ofcompression units capable of varying capacity thereof and of using analternative refrigerant.

A typical multi-stage rotary compressor has a plurality of compressionunits for sucking, compressing and discharging a refrigerant,respectively; and a driving unit for driving the compression units, allof which are accommodated in a sealed container.

In the compression unit, a plurality of eccentric cams are integrallyformed at a rotating shaft rotated by the driving unit. A rolling pistonis fit-fixed to an outer circumferential surface of each eccentric cam.The rolling piston is positioned in a cylinder and rolledly-moved whenit is contact with an inside diameter of the cylinder. The cylinder isdivided therein into a suction chamber and a compression chamber by avane contacting the rolling piston. The driving unit is composed of amotor for rotating the rotating axis, and accommodated in the sealedcontainer together with the compression unit.

This typical multi-stage rotary compressor sequentially performssuction, compression and discharge of a refrigerant when the rollingpiston is contact with the inside diameter of the cylinder at one point.If respective compression units are driven, a great deal of load isgenerated thereby to obtain a great capacity (hereinafter, referred to apower mode). At this time, the capacity of the compressor may correspondto the sum of refrigerants discharged from the respective compressionunits. If it is expected that the load is decreased thereby to obtainless capacity and power saving effect (hereinafter, referred to a savingmode), it may be achieved by cutting off the refrigerants sucked inseveral compression units, or by idling the rolling piston withoutallowing the compression of the refrigerant by means of moving the vaneback and fixing it with such as a piece thereby to remove a boundarybetween the suction chamber and the compression chamber.

Or, the capacity of the refrigerant may be varied by speed variationusing an inverter motor having a control drive as a driving unit.

The structure of the typical rotary compressor and a driving methodtherefor have the following problems.

First, in case of cutting off a refrigerant sucked in the compressionunit, various capacity variation may not be implemented.

Second, during the saving mode in process, the method of moving back andfixing the vane requires an additional component like the piece and aspace to install it, and increases the number of manufacturingprocesses.

Third, as the piece repeatedly impacts on the vane, it may result indamaging a surface thereof as the time elapses, and cause abrasion orgeneration of impurity thereby to degrade reliability of the compressor.

Fourth, in cases of idling the rolling piston or cutting off a suctionof the refrigerant, because several compression units are not used, itmay degrade efficiency of the compressor.

Fifth, in case of using the inverter motor as the driving unit, itrequires generally a high price so as to increase manufacturing costs.Therefore, there is a need for realizing a capacity variation even usinga constant-seed motor which requires relatively low price.

DISCLOSURE OF INVENTION Technical Problem

Therefore, it is an object of the present invention to provide amulti-stage rotary compressor capable of maximizing a compressionefficiency, even using a plurality of compression units al together, andof decreasing power consumption to be suitable for a saving mode.

Technical Solution

To achieve these objects, there is provided a multi-stage rotarycompressor, comprising: a casing having a sealed space therein; adriving unit installed in the casing, for generating a driving force; aplurality of compression units for receiving the driving force from thedriving unit and compressing a refrigerant; and a connection unit forconnecting the plurality of compression units and guiding therefrigerant discharged from a compression unit to be sucked directlyinto the neighboring compression unit and then to be re-compressed.

DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view showing a first embodiment in accordance withthe present invention;

FIG. 2 is a sectional view showing a second embodiment in accordancewith the present invention;

FIG. 3 is a sectional view showing a third embodiment in accordance withthe present invention;

FIG. 4 is a sectional view showing an operation of a power mode inaccordance with the third embodiment of the present invention;

FIG. 5 is a sectional view showing an operation of a saving mode inaccordance with the third embodiment of the present invention;

FIG. 6 is a sectional view showing a fourth embodiment in accordancewith the present invention; and

FIG. 7 is a graph showing a volume ratio of a cylinder and a compressionefficiency according to the present invention.

BEST MODE

FIG. 1 is a sectional view showing a first embodiment in accordance withthe present invention;

FIG. 2 is a sectional view showing a second embodiment in accordancewith the present invention;

FIG. 3 is a sectional view showing a third embodiment in accordance withthe present invention;

FIG. 4 is a sectional view showing an operation of a power mode inaccordance with the third embodiment of the present invention;

FIG. 5 is a sectional view showing an operation of a saving mode inaccordance with the third embodiment of the present invention;

FIG. 6 is a sectional view showing a fourth embodiment in accordancewith the present invention; and

FIG. 7 is a graph showing a volume ratio of a cylinder and a compressionefficiency according to the present invention.

INDUSTRIAL APPLICABILITY

As described so far, the multi-stage rotary compressor according to thepresent invention has effects as follows.

First, by re-compressing a previously-compressed refrigerant, a highdischarge pressure can be obtained and a volume efficiency can beimproved. Also, a leakage into a casing can be reduced and a heatquantity transferred to a low temperature refrigerant of a suction sidecan be remarkably decreased by using the previously compressedrefrigerant during the re-compression.

Second, the present invention does not need an additional component anda space to install it in comparison with a method in which a vane ismoved back and fixed during a saving mode in process, therebysimplifying manufacturing processes. Also, because a piece for movingback and fixing the vane is not required, there can not be no problemrelated to abrasion, a generation of impurity, and the like, therebyimproving reliability of the compressor.

Third, by using every plurality of compression units during the savingmode, efficiency of a motor or the compressor can be improved.Furthermore, compared with a power mode, since the previously-compressedrefrigerant is re-compressed, power requirement becomes less, whichresults in a power saving effect.

Fourth, manufacturing costs can be reduced by varying capacity using alow price of a constant-speed motor.

1. A multi-stage rotary compressor, comprising: a casing having a sealedspace therein; a driving unit installed in the casing, for generating adriving force; a first compression unit and a second compression unitfor receiving the driving force from the driving unit and compressing arefrigerant; and a connection unit for connecting the first and secondcompression units and guiding the refrigerant discharged from the secondcompression unit to be sucked directly in the first compression unit andthen re-compressed.
 2. The compressor of claim 1, wherein the drivingunit is formed as a constant-speed motor.
 3. The compressor of claim 1,wherein the first compression unit and the second compression unit havea different size of an inner space for sucking and compressing acompressed refrigerant, respectively.
 4. The compressor of claim 3,wherein a volume ratio between the volume of the inner space of acylinder of the second compression unit and the volume of the innerspace of the cylinder of the first compression unit is 1:0.5-0.8.
 5. Thecompressor of claim 4, wherein a volume ratio between the volume of theinner space of the cylinder of the second compression unit and thevolume of the inner space of the cylinder of the first compression unitis 1:0.6-0.65.
 6. The compressor of claim 1, wherein the connection unitcomprises: a suction pipe for guiding a refrigerant to a compressionunit; a chamber for covering a discharge valve of the second compressionunit and then temporally storing the refrigerant discharged from thesecond compression unit; and a first connection passage for guiding therefrigerant from the chamber to the first compression unit.
 7. Thecompressor of claim 6, wherein the chamber is installed at a lowerportion of the compression unit for preventing a leakage of therefrigerant with maintaining a sealed state thereof.
 8. The compressorof claim 6, the first connection passage sequentially penetrates abearing supporting the second compression unit in an axial direction anda side surface of the cylinder of the first compression unit in adirection of a radius thereof, and then is connected to the inner spaceof the first compression unit.
 9. The compressor of claim 6, wherein thefirst connection passage penetrates the casing thereby to be exposed tothe external and then again penetrates the casing and the cylinder ofthe first compression unit in a direction of a radius thereof,thereafter being connected to the inner space of the first compressionunit.
 10. The compressor of claim 1, wherein the connection unitcomprises: a suction pipe for guiding a refrigerant to the secondcompression unit to compress the refrigerant; a first chamber forcovering a discharge valve of the second compression unit and temporallystoring the refrigerant discharged from the second compression unit; asecond chamber for receiving the refrigerant from the first chamber andtemporally storing the refrigerant; a first connection passage forguiding the refrigerant from the first chamber to the second chamber;and a second connection passage for guiding the refrigerant from thesecond chamber to the first compression unit.
 11. The compressor ofclaim 10, wherein the first chamber and the second chamber arepositioned at a lower portion of the second compression unit and anupper portion of the first compression unit, respectively, therebypreventing a leakage of the refrigerant with maintaining a sealed statethereof.
 12. The compressor of claim 11, wherein the first connectionpassage penetrates a bearing supporting the compression unit and acylinder of each compression unit in an axial direction.
 13. Thecompressor of claim 11, wherein the second connection passage covers anupper portion of the second compression unit, penetrates an upperbearing, and then connects the second chamber to the inner space of thefirst compression unit.
 14. The compressor of claim 1, wherein theconnection unit selectively guides the refrigerant in order for therefrigerant discharged from the second compression unit to be suckeddirectly into the first compression unit thereafter to be compressed orto be compressed one time at each compression unit, and then discharged.15. The compressor of claim 14, wherein the connection unit comprises: afirst suction pipe for guiding the refrigerant to the first compressionunit; a first control valve mounted on the first suction pipe, forcontrolling the sucked refrigerant; a second suction pipe for guidingthe refrigerant to the second compression unit; a chamber for covering asecond discharge valve which controls a discharged refrigerant of thesecond compression unit and temporally storing the refrigerantdischarged from the second compression unit; a second control valve foradjusting a flow direction of the refrigerant; a first connection pipefor connecting the chamber to the second control valve; a secondconnection pipe for connecting the second control valve to the firstconnection pipe to guide the refrigerant to the first compression unit;and a third connection pipe for connecting the second control valve tothe casing to guide the refrigerant to the inner space of the casing.16. The compressor of claim 16, wherein suction sides of the first andsecond suction pipes are connected to an accumulator separatinggas-liquid of the refrigerant, respectively.
 17. The compressor of claim15, wherein only one of the first and second suction pipes is connectedto the accumulator.
 18. The compressor of claim 15, wherein the secondcontrol valve is a pilot valve.